Boss Tosk was a crime lord and leader of the Jalk Syndicate during the Galactic Civil War. He was a Columi and as such had a large overdeveloped head with bulbous eyes and a diminutive body. He achieved locomotion by the use of a repulsorsuit and the help of numerous assassin droids.

The Jalk Syndicate operated in the Tapani sector and Boss Tosk's hideout was located in the Cor III system, Barnaba Province. The Tosk was a solitary individual and preferred to seek seclusion in this hideout where he controlled the operations of the syndicate using super computers and with the help of numerous servant and worker droids. These droids performed the tasks that Boss Tosk was not able to physically perform due to the weakness of his frail body.

With the apparent fall of the Mecrosa Order, the Jalk Syndicate rose to take their place as House Mecetti's primary underground operator. With the rise of the Empire, house Mecetti, eager to impress, paid Boss Tosk to close his operation down. The Tosk feigned the shutdown of his operations but in reality he forged a new alliance with House Barnaba.